1. Technical Field
This invention relates to a propeller shaft arrangement connecting a transmission and a differential gear of an automobile, and more particularly to a propeller shaft arrangement, most of which is made of aluminum.
2. Background Art
A propeller shaft for an automobile is generally made of steel and connects a transmission with a differential gear. Generally, the propeller shaft has a universal joint since the vibration system on the transmission side and that on the differential gear side differ from each other. If a universal joint is provided, the propeller shaft is divided into two segments and these two segments are supported by a center bearing mounted on the vehicle body.
Recently, there has been a demand to reduce weight of the propeller shaft and experiments have been made using aluminum-made propeller shafts.
However, since aluminum is weaker than steel, the diameter of the propeller shaft must be increased to insure sufficient strength. A larger center bearing is required to support a propeller shaft having a larger diameter. Further, circumferential speed of the propeller shaft is raised as its diameter becomes greater. The center bearing (ball bearing) may not be able to cope with such increased circumferential speed. In addition, an oil seal which protects the center bearing from dust and water may not function appropriately if a large center bearing is employed. In this case, the center bearing and the aluminum propeller shaft may contact each other directly and abrasion is accelerated.